Calliper System for Laying Out Stirrups Used in Lower Extremity Orthosis

1. Field of the Invention

The present invention relates to a method of laying out a foundation stirrup for a lower extremity orthosis so that the mechanical axis of the stirrup coincides with the anatomical ankle joint and to a calliper useful therein.

The laying out of a foundation stirrup involves the finding of two essential points on the stirrup: the vertical and longitudinal center lines and the mid-point between the stirrup joint holes. When these points have been located on the stirrup, measurements can be taken from the mid-point to locate exactly where the stirrup should be bent in order to fit the orthosis assembly. For patients with a varus or valgus deformity (ankle turned in or out), the deformity needs to be noted on the stirrup when measuring for the bend points in order to assist in the correction of the deformity.

2. Description of the Prior Art

There is no known prior art directly related to the mechanical or automatic measuring of a stirrup to determine its bend points or lines. Devices are known for the correction and improvement of faulty foot posture in a patient through alignment of the feet by measurement of the degree of fault found in the patient's feet, for the purpose of making a wedge for insertion into a corrective shoe; see U.S. Pat. No. 2,492,059 to G. Ogden issued Dec. 20, 1949. Stirrups and the orthotic devices for which they comprise the foundation of are, of course, known as well, see e.g. U.S. Pat. No. 3,732,861 to H. Lehneis, issued May 15, 1973.

The conventional prior art tools used to lay out a stirrup for measurement are a ruler, grease pencil and a straight edge. For a normal foot, the vertical (lateral) and longitudinal center lines are layed out with the ruler and pencil and the mid-point between the joint holes of the stirrup is thus designated. Where a varus or valgus deformity is present, the stirrup must be manually measured in this fashion so that it may be off-set to one side of the foot or the other when bent. A center hole, either at the intersection of the vertical and longitudinal center-lines, or off-set in the case of a deformity, is then drilled. In order to measure the bend points and form the stirrup, the medial lateral width of the shoe at the heel breast is measured and increased by a width of an inch. This dimension is then manually marked equally on each side of the drilled center hole. The stirrup is then transferred to a stirrup bender in order to form the stirrup bends from the measurement taken.

Laying out a stirrup in the above mentioned manner is very time consuming, tedious and often inaccurate, particularly under the pressure of a large volume of work to be completed.

If the stirrup is not laid out correctly, the following problems often arise: binding and excessive wear at the mechanical joint, rapid tiring of the patient's leg due to the muscular effort the patient must expend in trying to overcome the defective mechanical joint, and even temporary or permanent damage to the patient's limb.

The present invention utilizes a calliper having an assembly of two bars which slide in and out of a main bar, the end bars being attached to the main bars by means of for example two internal springs extending laterally from a center pin in the main bar to a pin near the end of each end bar. Each end bar has a dowel extending down from its underside. The assembly is fitted over an unbent, flat stirrup by placing the end bar dowels into the stirrup joint holes. The two internal springs being of equal tension, the floating main bar is automatically thus positioned in the exact center of the stirrup. The two pins on the end bars and the pin in the main bar line up automatically on the center-line of the joint holes, and thus the calliper assembly of the invention finds the exact vertical and longitudinal center-lines and the mid point between the joint holes on the stirrup. The assembly can be adjusted to accomodate stirrup sizes ranging from, for example, six inches to ten-and-a-quarter inches (6" to 101/4"). By utilizing the scales on the front of the end bars, the necessary degree of off-set for positioning the adjusted center hole" in the case of a valgus or varus deformity can be measured. These end bar scales also enable the invention to be used without the internal main bar springs. One the "stirrup calliper" is placed on a stirrup and the floating main bar is in position, thumb screws on the main bar are locked down and a soft-face hammer is then used to tap lightly the center pin punch to mark the center hole and, if desired, also the lateral axis on the stirrup by using end pin punches.

Applicant's "Stirrup Calliper" thus provides an easily-utilized and highly accurate mechanical means for taking and marking automatic stirrup measurements which otherwise must be done laboriously by hand, subject to the inaccuracies of human error.

For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals and wherein:

FIG. 1 is an external, side view of the "stirrup calliper" assembly used in the preferred embodiment of the present invention;

FIG. 2 is an internal, cross-sectional, side view of the "stirrup calliper" assembly of FIG. 1 showing the connection of the end bars to the floating center bar by means of the lateral internal springs;

FIG. 3 is a top view of the "stirrup calliper" assembly of FIG. 1 placed atop an exemplary nine-and-a-half inch (91/2") unbent stirrup for measurement purposes; and

FIG. 4 is an isometric view of the completed, bent stirrup after the measurements have been taken and marked, the "stirrup caliper" removed and the stirrup properly bent into position for use on the patient.

As shown in the side views of FIGS. 1 and 2 and the top view in FIG. 3, the main floating bar 2 of the exemplary preferred embodiment of the calliper 1 is a hollow rectangular tube approximately 5 3/16" in width, 3/441 in height and an inch in depth. Extending point downwardly through the center of the main bar 2 is a metal marking or punch pin of approximately 1/16" diameter having a marking point 4a. Two thumb screws 8 are attached to the top of the main bar 2, one at either end as shown best in the cross-sectional view of FIG. 2.

Two lateral springs 3 are attached at their proximal ends to the center pin 4 in the main bar 2 and extend out from either side. Both springs 3 are of equal tension.

Each end bar 10 is also a hollow rectangular tube of slightly smaller dimension than the main floating bar 3 and approximately 33/8" in width. The opposed, extended end bars 10 nest and fit inside the open ends of the floating main bar 2 extending out freely, as indicated by the arrows in FIG. 1. Each end bar 10 has a pin 5 running downwardly through it about three-quarters of the way to the end of the bar 10.

The distal end of each spring 3 is attached to its respective end bar pin 5. Rather than as illustrated, the two end bar pins 5, like the main bar center pin 4, can be made to extend out from the bottoms and tops of the end bars 10 the same distance (see lined phantom additions 5a) and then also be used as marking or punch pins 5a for setting and marking the lateral center-line of the stirrup. The cross-sectional view of FIG. 2 best illustrates the internal, telescoping or nesting assembly of the three bars 2, 10 via the two springs 3. A dowel 6 approximately 3/8" in diameter extends downwardly from each end of the end bars 10. These anchoring dowels 6 are positioned next to the end bar pins 5 and extend downwardly approximately 3/32 of an inch further than do the pins 5 if they were made to also function as marking pins 5a.

A measurement scale 7 is etched into the front of each of the end bars 10, as seen in FIG. 1. By sliding the two end bars 10 in or out of the main bar 2 as needed, the entire calliper assembly can be adjusted to accomodate stirrup sizes ranging from 6" to 101/4'.

As shown in FIG. 3, the entire calliper assembly is placed atop a flat, unbent stirrup 15 by means of placing the anchoring dowels 6 extending downward from each of the end bars 10 into the two joint holes 13 at either ends of the flat stirrup 15, anchoring the two end bars 10 to the stirrup 15. Once the assembly is so in place atop the stirrup 15, the floating main bar 2 is automatically positioned uner the equal actions of the springs 3 in the exact center of the stirrup 15, with the center pin 4 pinpointing the location of the center-point on the stirrup 15. The exact, vertical, center-line on the stirrup 15 is thus determined. The center pin 4 also aligns automatically with the two end bar pins 5, thus determining the longitudinal center-line on the stirrup 15.

If a varus or valgus deformity exists which the stirrup 15 is to correct, measurements to place the mid-point between the joint holes determined by the center pin 4 off-centered to the necessary degree can be taken with the use of the calibrating scales 7 on the end bars 10. The thumb screws 8 on the main bar 2 are then locked down to securely clamp the main bar 2 to the end bars 10.

A soft-face hammer (note FIG. 2) is then used to tap lightly on the center pin 4, driving it vertically downwardly to physically mark the mid-point 11 on the tongue section 9 of the stirrup 15 as measured between the joint holes 13, and also to tap on the end pins 5 (if they are made for marking) to mark the points defining the vertical or lateral center-line of the stirrup 15.

The "stirrup calliper" 1 is then removed from the stirrup 15 and measurements can be taken from the mid-point 11 determined and marked by the "stirrup calliper" 1 along the lateral center-line of the stirrup 15 to find the bending lines 14, 16 for the stirrup arms 12.

The "stirrup calliper" 1 can also function without the two internal springs 3 simply by placing the assembly onto the stirrup is in the same manner as would be done with the springs and using the measurement scales 7 to determine the exact center placement of the main bar 2. The scales 7 can of course also be used to double-check the proper center placement of the main floating bar 2 by the spring 3, and then used as a guide for the proper placement should the springs system not be properly working.

After the bend lines 14, 16 have been determined, the arms 12 of the stirrup 15 are bent into the desired configuration, all as well known in the prior art, to produce the bent arm 12A of the final bent stirrup 15A shown is FIG. 4. The bent stirrup in then ready for final, ultimate use by the patient as a lower extremity orthosis. For a further understanding of the details of the bending aspects of the final stirrup 15A, reference is had to pages 244-248 of the medical text "A Manual of Lower Extremities Orthothics" published by Charles C. Thomas, Banerstone House, (Springfield, IL) written by Clausen F. Englad, et al and edited by Miles H. Anderson, which text is incorprated herein by reference.

Because of the varying embodiments that may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment detailed herein in accordance with the descriptive requirements of the law (such as shape of the three bars), it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.